Storage battery control device

ABSTRACT

A current of a storage battery is appropriately controlled depending on the situation. In a battery controller, a battery information acquiring unit acquires information on the storage battery. A first allowable current calculating unit calculates a first allowable current of a battery module in accordance with a rated value of a component through which a current flows by charging or discharging of the battery module. A second allowable current calculating unit calculates a second allowable current of the battery module in accordance with an SOC of the battery module on the basis of the information acquired by the battery information acquiring unit. A third allowable current calculating unit calculates a third allowable current of the battery module in accordance with an SOH of the battery module on the basis of the information acquired by the battery information acquiring unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/741,784, filed Jan. 4, 2018, which is a 371 of InternationalApplication No. PCT/JP2016/073215, filed Aug. 8, 2016, which claims thepriority of Japanese Patent Application No. 2015-177561, filed Sep. 9,2015, the disclosure of which are expressly incorporated by referenceherein.

TECHNICAL FIELD

The present invention relates to a storage battery control device.

BACKGROUND ART

Conventionally, in-vehicle battery systems, mounted on a hybrid electricvehicle (HEV) or a plug-in hybrid electric vehicle (PHEV) and using alithium ion secondary battery as a storage battery, are in use. In suchin-vehicle battery systems, it is necessary to limit the current flowingin a storage battery within a predetermined range from the perspectiveof safety of components and deterioration prevention. For example, PTL 1discloses a technique for setting an upper limit value of the current inaccordance with the degree of deterioration of a storage battery.

CITATION LIST Patent Literature

PTL 1: International Publication No. 2013-094057

SUMMARY OF INVENTION Technical Problem

The magnitude of a current to be output from an in-vehicle batterysystem varies depending not only on the degree of deterioration of astorage battery but also on the situation. For example, depending on thetraveling state or other conditions of a vehicle, it may be necessary totemporarily supply a large current to a load. In such a case, it ispreferable to temporarily raise the upper limit value of the currentsince the influence on deterioration of the storage battery is small ifit is a short time. However, in the conventional technique described inPTL 1, the upper limit value of the current is set in accordance withthe degree of deterioration of the storage battery, and thus it isdifficult to appropriately control the current of the storage batterydepending on the situation.

Solution to Problem

A storage battery control device according to the present inventionincludes: a battery information acquiring unit for acquiring informationon a storage battery; a first allowable current calculating unit forcalculating a first allowable current of the storage battery inaccordance with a rated value of a component through which a currentflows by charging or discharging of the storage battery; a secondallowable current calculating unit for calculating a second allowablecurrent of the storage battery in accordance with a charging state ofthe storage battery on the basis of the information acquired by thebattery information acquiring unit; and a third allowable currentcalculating unit for calculating a third allowable current of thestorage battery in accordance with a deterioration state of the storagebattery on the basis of the information acquired by the batteryinformation acquiring unit.

Advantageous Effects of Invention

According to the present invention, it is possible to appropriatelycontrol the current of a storage battery depending on the situation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a battery system towhich a storage battery control device according to an embodiment of thepresent invention is applied.

FIG. 2 is a functional block diagram of a battery controller.

FIG. 3 is a functional block diagram of a first allowable currentcalculating unit.

FIG. 4 is a diagram explaining a method of determining a first allowablecurrent.

FIG. 5 is a functional block diagram of a second allowable currentcalculating unit.

FIG. 6 is a diagram explaining a method of determining a secondallowable current.

FIG. 7 is a functional block diagram of a third allowable currentcalculating unit.

FIG. 8 is a diagram explaining a method of determining a third allowablecurrent.

FIG. 9 is a flowchart of charge/discharge control of a battery module.

FIG. 10 is a diagram illustrating an example of a change in an allowablecurrent in the case of using a conventional technique.

FIG. 11 is a diagram illustrating an example of a change in an allowablecurrent in the case of using the present invention.

FIG. 12 is a diagram illustrating an example of a change in an allowablecurrent in a case where the present invention is more proactivelyutilized.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described below withreference to the drawings.

FIG. 1 is a diagram illustrating a configuration of a battery system towhich a storage battery control device according to an embodiment of thepresent invention is applied. The battery system 100 illustrated in FIG.1 is connected to an inverter 110 and a host controller 112. A load 111is connected to the inverter 110.

The inverter 110 is a bidirectional inverter that operates under thecontrol of the host controller 112. The inverter 110 converts DC powersupplied from the battery system 100 into AC power and outputs the ACpower to the load 111. The load 111 is, for example, a three-phase ACmotor mounted on a vehicle and generates a driving force of the vehicleby being rotationally driving using the AC power supplied from theinverter 110. In addition, when regenerative power generation isperformed by allowing the load 111 to operate as a generator usingkinetic energy of the vehicle, AC power is output from the load 111. Inthis case, the inverter 110 converts the AC power output from the load111 into DC power, and outputs the obtained DC power to the batterysystem 100 for storage. In this manner, by operating the inverter 110according to the control of the host controller 112, the battery system100 is charged or discharged.

Note that the present invention is not limited to the configurationillustrated in FIG. 1 as long as charging and discharging of the batterysystem 100 can be appropriately controlled. For example, anothercharging system different from the inverter 110 may be connected to thebattery system 100, and charging of the battery system 100 may beperformed as needed using this charging system.

The battery system 100 includes a battery module 101, a current sensor102, a voltage sensor 103, a temperature sensor 104, a leakage currentsensor 105, a relay 106A, a relay 106B, and a battery controller 107.

The battery module 101 is a chargeable/dischargeable storage batteryformed by connecting a plurality of unit batteries in series or inseries and in parallel. Note that the battery module 101 may be dividedinto two or more groups, and a breaker which can be manually operatedmay be included between the groups. With this arrangement, it ispossible to prevent occurrence of an electric shock accident or ashort-circuit accident by opening the breaker at the time of work suchas assembling, disassembling, inspection, etc. of the battery system100.

The current sensor 102 detects a charge/discharge current flowing in thebattery module 101. The voltage sensor 103 detects the voltage of thebattery module 101. The temperature sensor 104 detects the temperatureof the battery module 101. The leakage current sensor 105 detects theinsulation resistance of the battery module 101. The detection resultsof the current sensor 102, the voltage sensor 103, the temperaturesensor 104, and the leakage current sensor 105 are separately output tothe battery controller 107.

The relays 106A and 106B are for switching electrical connection statesbetween the battery module 101 and the inverter 110, and are controlledby the battery controller 107 or the host controller 112. The relay 106Ais connected between a positive electrode side of the battery module 101and the inverter 110, and the relay 106B is connected between a negativeelectrode side of the battery module 101 and the inverter 110. Note thateither one of the relays 106A and 106B may be omitted. In order to limitan inrush current, a precharge relay and a resistor may be included inparallel with the relay 106A or 106B. In this case, at the time ofconnecting the battery module 101 and the inverter 110, it is onlyrequired to turn on the precharge relay first and, after the currentbecomes sufficiently small, to turn on the relay 106A or 106B and toturn off the precharge relay.

The battery controller 107 corresponds to the storage battery controldevice according to an embodiment of the present invention. The batterycontroller 107 acquires the respective detection results of the currentsensor 102, the voltage sensor 103, the temperature sensor 104, and theleakage current sensor 105 and controls the battery system 100 on thebasis of these detection results. For example, the battery controller107 calculates the state of charge (SOC) or the state of health (SOH) ofthe battery module 101 on the basis of the detection result of acharge/discharge current by the current sensor 102 or the detectionresult of a voltage by the voltage sensor 103. Based on thesecalculation results, charge/discharge control of the battery module 101and balancing control for equalizing SOCs of the respective unitbatteries of the battery module 101 are performed. The batterycontroller 107 further determines whether the battery module 101 is in aleakage state or in a state where it is likely to leak on the basis ofthe detection result of the insulation resistance by the leakage currentsensor 105. When determining that the battery module 101 is in one ofthese states, the battery controller 107 stops operation of the batterysystem 100. Other than the above, the battery controller 107 can executevarious processing.

Note that, in the charge/discharge control of the battery module 101,the battery controller 107 calculates an allowable current forappropriately controlling the current flowing in the battery module 101depending on the situation and outputs the allowable current to the hostcontroller 112. Details of the charge/discharge control of the batterymodule 101 by the battery controller 107 will be described later indetail.

The host controller 112 controls an operation state of the batterysystem 100 or the inverter 110 on the basis of various information ofthe battery module 101 transmitted from the battery controller 107.

Next, details of the charge/discharge control of the battery module 101by the battery controller 107 will be described. FIG. 2 is a functionalblock diagram of the battery controller 107. As illustrated in FIG. 2 ,the battery controller 107 includes respective functional blocksincluding a battery information acquiring unit 201, a first allowablecurrent calculating unit 202, a second allowable current calculatingunit 203, a third allowable current calculating unit 204, and anallowable current selecting unit 205. The battery controller 107 canimplement these functional blocks for example by executing apredetermined program by a CPU.

The battery information acquiring unit 201 acquires various informationon the state of the battery module 101 on the basis of the respectivedetection results of the current sensor 102, the voltage sensor 103, andthe temperature sensor 104. The battery information acquiring unit 201acquires, for example, the charge/discharge current of the batterymodule 101 detected by the current sensor 102, the temperature of thebattery module 101 detected by the temperature sensor 104, and the likeas information of the battery module 101. Moreover, it is also possibleto acquire use time of the battery module 101 measured by using a timer(not illustrated) incorporated in the battery controller 107, atraveling distance of the vehicle on which the battery module 101 ismounted, or other information as the information of the battery module101. That is, the battery information acquiring unit 201 can acquire atleast one piece of information from among the various informationrelating to the state of the battery module 101 as described above. Notethat information other than those mentioned above may be acquired as theinformation of the battery module 101.

The first allowable current calculating unit 202 calculates a firstallowable current of the battery module 101. The first allowable currentan allowable current of the battery module 101 in accordance with arated value of a component through which a current flows by charging ordischarging of the battery module 101. Note that a specific method ofcalculating the first allowable current by the first allowable currentcalculating unit 202 will be described later with reference to FIGS. 3and 4 .

The second allowable current calculating unit 203 calculates a secondallowable current of the battery module 101 on the basis of theinformation of the battery module 101 acquired by the batteryinformation acquiring unit 201. The second allowable current is anallowable current of the battery module 101 in accordance with the SOCof the battery module 101. Note that a specific method of calculatingthe second allowable current by the second allowable current calculatingunit 203 will be described later with reference to FIGS. 5 and 6 .

The third allowable current calculating unit 204 calculates a thirdallowable current of the battery module 101 on the basis of theinformation of the battery module 101 acquired by the batteryinformation acquiring unit 201. The third allowable current is anallowable current of the battery module 101 in accordance with the SOHof the battery module 101. Note that a specific method of calculatingthe third allowable current by the third allowable current calculatingunit 204 will be described later with reference to FIG. 7 .

The allowable current selecting unit 205 selects one of the firstallowable current, the second allowable current, and the third allowablecurrent calculated by the first allowable current calculating unit 202,the second allowable current calculating unit 203, and the thirdallowable current calculating unit 204, respectively. Note that aspecific method of selecting an allowable current by the allowablecurrent selecting unit 205 will be described later. Then, a value of theselected allowable current is output to the host controller 112. Whenthe allowable current is output from the allowable current selectingunit 205, the host controller 112 controls the battery system 100 andthe inverter 110 in accordance with the value of the allowable currentto perform charge/discharge control of the battery module 101.

Next, a method of calculating the first allowable current by the firstallowable current calculating unit 202 will be described. FIG. 3 is afunctional block diagram of the first allowable current calculating unit202. As illustrated in FIG. 3 , the first allowable current calculatingunit 202 includes respective functional blocks including a rated valueacquiring unit 301 and a first allowable current determining unit 302.

The rated value acquiring unit 301 acquires, as a rated value related tothe first allowable current, a rated current value of each componentsthrough which a current flows by charging or discharging of the batterymodule 101 out of various electric components forming the battery system100. For example, the rated value acquiring unit 301 acquires a ratedcurrent value of various components such as a bus bar, a connector, acurrent cable, a relay (switch), a fuse, or a screw arranged on the pathof charging/discharging current in the battery system 100. Note that ina case where a shunt resistor, adhesive resin, or the like is arrangedon a path of the charge/discharge current, the rated value acquiringunit 301 also acquires these rated current values. For example, therated value acquiring unit 301 prestores a temperature characteristic ofa rated current value of each component. The temperature of eachcomponent is estimated on the basis of the temperature of the batterymodule 101 detected by the temperature sensor 104, and then a ratedcurrent value corresponding to the temperature is acquired for eachcomponent. At this time, furthermore, a deterioration state of eachcomponent may be estimated on the basis of a use history of the batterysystem 100, and a rated current value of each component may bedetermined in consideration of the estimation result.

The first allowable current determining unit 302 determines the firstallowable current on the basis of the rated current value of eachcomponent acquired by the rated value acquiring unit 301. For example,the first allowable current determining unit 302 determines the firstallowable current in accordance with a component having the smallestrated current value.

FIG. 4 is a diagram explaining a method of determining the firstallowable current by the first allowable current determining unit 302.In FIG. 4 , each of straight lines 401, 402, and 403 represents acharacteristic example of a rated current value with respect toenergizing time of a component different from each other. The componentsof the battery system 100 include, in a mixed manner, a rated currentvalue being constant irrespective of energizing time as illustrated bythe straight line 401 and those whose rated current value decreases asenergizing time becomes longer (as an energizing duty becomes larger) asseparately illustrated by the straight lines 402 and 403. In a casewhere these rated current values are acquired by the rated valueacquiring unit 301, the first allowable current determining unit 302 candetermine the first allowable current according to a characteristic of arated current value with respect to energizing time as indicated by apolygonal line 404, for example.

Next, a method of calculating the second allowable current by the secondallowable current calculating unit 203 will be described. FIG. 5 is afunctional block diagram of the second allowable current calculatingunit 203. As illustrated in FIG. 5 , the second allowable currentcalculating unit 203 includes respective functional blocks including anSOC calculating unit 501, an internal resistance calculating unit 502,and a second allowable current determining unit 503.

The SOC calculating unit 501 calculates an SOC of the battery module 101on the basis of the detection result of a charge/discharge current bythe current sensor 102 or the detection result of a voltage by thevoltage sensor 103. For example, the SOC calculating unit 501 can derivean SOC from an integrated value of charging or discharging currents orderive an SOC from an open circuit voltage (OCV) when the battery module101 is not charged/discharged.

The internal resistance calculating unit 502 calculates an internalresistance value of the battery module 101 on the basis of the SOCderived by the SOC calculating unit 501. The internal resistancecalculating unit 502 can calculate the internal resistance value of thebattery module 101 on the basis of the OCV derived from the SOC, thedetection result of the charge/discharge current by the current sensor102, and the voltage detection result at the time of charging ordischarging by the voltage sensor 103. At this time, the internalresistance value of the battery module 101 may be derived inconsideration of the temperature detected by the temperature sensor 104.

The second allowable current determining unit 503 determines the secondallowable current on the basis of the SOC derived by the SOC calculatingunit 501 and the internal resistance derived by the internal resistancecalculating unit 502.

FIG. 6 is a diagram explaining a method of determining the secondallowable current by the second allowable current determining unit 503.In FIG. 6 , a curve 601 illustrates an example of an SOC-OCV curverepresenting the relationship between the SOC and the OCV of the batterymodule 101. When the maximum value and the minimum value of the SOC inwhich the battery module 101 is used are denoted by Smax and Smin,respectively, the maximum value Vmax and the minimum value Vmin of theOCV of the battery module 101 are derived as points corresponding toSmax and Smin on the SOC-OCV curve 601 as illustrated in FIG. 6 .

Here, when values of the SOC and the OCV at desired time t arerepresented as S(t) and V(t), respectively, these values can berepresented by a point on the SOC-OCV curve 601, for example, a point602. When a charge allowable current and a discharge allowable currentof the battery module 101 at this time are denoted by Ic(t) and Id(t),respectively, a relationship as illustrated in FIG. 6 holds between thepoint 602 and these currents. In FIG. 6 , R(t) represents the internalresistance of the battery module 101 at time t.

The above relationship is represented by the following mathematicalformula (1).

$\begin{matrix}{\begin{matrix}{{V(t)} = {{Vmax} - {{Ic}(t)}}} \\{= {{Vmin} + {{{Id}(t)} \times {R(t)}}}}\end{matrix}\quad} & (1)\end{matrix}$

From the mathematical formula (1), the following mathematical formulas(2) and (3) are derived as equations for deriving a charge allowablecurrent Ic(t) and a discharge allowable current Id(t).Ic(t)={V max−V(t)}/R(t)  (2)Id(t)={V(t)−V min}/R(t)  (3)

The second allowable current determining unit 503 can determine thesecond allowable current by deriving the charge allowable current Ic(t)and the discharge allowable current Id(t) on the basis of the abovemathematical formulas (2) and (3), respectively.

Next, a method of calculating the third allowable current by the thirdallowable current calculating unit 204 will be described. FIG. 7 is afunctional block diagram of the third allowable current calculating unit204. As illustrated in FIG. 7 , the third allowable current calculatingunit 204 includes respective functional blocks including an SOHcalculating unit 701, a lifetime predicting unit 702, and a thirdallowable current determining unit 703.

The SOH calculating unit 701 calculates an SOH of the battery module 101on the basis of the detection result of a charge/discharge current bythe current sensor 102 or the detection result of a voltage by thevoltage sensor 103. Note that the calculation results of the SOC and theinternal resistance may be acquired from the second allowable currentcalculating unit 203, and the SOH may be calculated on the basis ofthese calculation results.

The lifetime predicting unit 702 predicts a lifetime of the batterymodule 101 on the basis of the SOH calculated by the SOH calculatingunit 701. The lifetime predicting unit 702 records a history of theinformation of the battery module 101 acquired by the batteryinformation acquiring unit 201 in association with the SOH of thebattery module 101, for example. Estimating the future transition of theSOH on the basis of the information recorded in this manner enablescalculating the deterioration progression speed of the battery module101 and predicting the lifetime from the calculation result.

The third allowable current determining unit 703 determines the thirdallowable current on the basis of the SOH derived by the SOH calculatingunit 701 and the lifetime derived by the lifetime predicting unit 702.The third allowable current determining unit 703 compares the lifetimeof the battery module 101 predicted by the lifetime predicting unit 702with a preset target lifetime value. As a result, if a deviation betweenthe target lifetime value and the predicted lifetime value is large, avalue of the third allowable current is adjusted such that the deviationbecomes smaller. As a result, the third allowable current calculatingunit 204 can calculate the third allowable current corresponding to theSOH of the battery module 101.

FIG. 8 is a diagram explaining a method of determining the thirdallowable current by the third allowable current determining unit 703.In FIG. 8 , a curve 801 illustrates an example of the relationshipbetween the deterioration progression speed and the third allowablecurrent. The third allowable current determining unit 703 stores data inwhich the relationship of FIG. 8 having been obtained in advance by atest or the like is mapped, for example. By using this data, the thirdallowable current determining unit 703 can determine the third allowablecurrent in accordance with the deterioration progression speed of thebattery module 101.

FIG. 9 is a flowchart of charge/discharge control of the battery module101 by the battery controller 107. The battery controller 107 executescharge/discharge control of the battery module 101 at everypredetermined processing cycle according to the flowchart of FIG. 9 .

In step S101, the battery controller 107 acquires the variousinformation of the battery module 101 as described above by the batteryinformation acquiring unit 201.

In step S102, the battery controller 107 calculates the first allowablecurrent of the battery module 101 on the basis of the information of thebattery module 101 acquired in step S101 by the first allowable currentcalculating unit 202.

In step S103, the battery controller 107 calculates the second allowablecurrent of the battery module 101 on the basis of the information of thebattery module 101 acquired in step S101 by the second allowable currentcalculating unit 203.

In step S104, the battery controller 107 calculates the third allowablecurrent of the battery module 101 on the basis of the information of thebattery module 101 acquired in step S101 by the third allowable currentcalculating unit 204.

In step S105, the battery controller 107 compares the calculationresults of steps S102 to S104 by the allowable current selecting unit205. That is, the first allowable current calculated in step S102, thesecond allowable current calculated in step S103, and the thirdallowable current calculated in step S104 are compared to grasp themagnitude relation among them.

In step S106, the battery controller 107 determines whether the firstallowable current is lower than both of the second allowable current andthe third allowable current on the basis of the comparison result ofstep S105 by the allowable current selecting unit 205. As a result, ifthe determination condition is satisfied, that is, if the firstallowable current is the lowest, the processing proceeds to step S109.On the other hand, if the determination condition is not satisfied, thatis, if the first allowable current is higher than at least one of thesecond allowable current and the third allowable current, the processingproceeds to step S106.

In step S107, the battery controller 107 determines whether the secondallowable current is lower than both of the first allowable current andthe third allowable current on the basis of the comparison result ofstep S105 by the allowable current selecting unit 205. As a result, ifthe determination condition is satisfied, that is, if the secondallowable current is the lowest, the processing proceeds to step S111.On the other hand, if the determination condition is not satisfied, thatis, if the second allowable current is higher than at least one of thefirst allowable current and the third allowable current, the processingproceeds to step S108.

In step S108, the battery controller 107 determines whetherdeterioration suppression of the battery module 101 is to be prioritizedin the current situation by the allowable current selecting unit 205.The allowable current selecting unit 205 determines that thedeterioration suppression of the battery module 101 is to be prioritizedin cases such as a case where a mode that gives priority to the lifetimeof the battery module 101 is set in the battery system 100 or a casewhere the load of the battery module 101 is small such as when thevehicle is traveling. On the other hand, the allowable current selectingunit 205 determines that the deterioration suppression of the batterymodule 101 is not to be prioritized in cases such as a case where a modethat gives priority to the traveling performance or fuel efficiency ofthe vehicle is set in the battery system 100 or when the load of thebattery module 101 is large such as during acceleration of the vehicle.As a specific example, a case is considered where the battery system 100is mounted in an electric vehicle such as a hybrid car. In such a case,when the vehicle travels on an approach road to a highway or on anuphill road or overtakes, a driver may presses on the accelerator pedaldeeper and request a higher output torque from the load 111 that is anelectric motor. If the allowable current selecting unit 205 hasdetermined whether the request for a higher output has been made anddetermined that the request for a higher output has been made on thebasis of an amount of change in the degree of accelerator opening, theallowable current selecting unit 205 can determine that thecharge/discharge performance of the battery module 101 is to beprioritized and that the deterioration suppression is not to beprioritized. Note that, other than the above, the determination in stepS108 can be performed using various determination conditions. As aresult, if it is determined that the deterioration suppression is to beprioritized, the processing proceeds to step S112. On the other hand, ifit is determined that the deterioration suppression is not to beprioritized, the processing proceeds to step S109.

In step S109, the battery controller 107 determines whether the firstallowable current is lower than the second allowable current on thebasis of the comparison result of step S105 by the allowable currentselecting unit 205. As a result, if the first allowable current is lowerthan the second allowable current, the processing proceeds to step S110.On the other hand, if the first allowable current is greater than orequal to the second allowable current, the processing proceeds to stepS111.

In step S110, the battery controller 107 selects the first allowablecurrent obtained in step S102 by the allowable current selecting unit205 and outputs the first allowable current to the host controller 112.That is, if the first allowable current is lower than the secondallowable current and the third allowable current, or if thedeterioration suppression is not to be prioritized and the firstallowable current is lower than the second allowable current, thebattery controller 107 executes step S110. As a result, the firstallowable current is selected as the allowable current in thecharge/discharge control of the battery module 101.

In step S111, the battery controller 107 selects the second allowablecurrent obtained in step S103 by the allowable current selecting unit205 and outputs the second allowable current to the host controller 112.That is, if the second allowable current is lower than the firstallowable current and the third allowable current, or if thedeterioration suppression is not to be prioritized and the secondallowable current is lower than the first allowable current, the batterycontroller 107 executes step S111. As a result, the second allowablecurrent is selected as the allowable current in the charge/dischargecontrol of the battery module 101.

In step S112, the battery controller 107 selects the third allowablecurrent obtained in step S104 by the allowable current selecting unit205 and outputs the third allowable current to the host controller 112.That is, if the deterioration suppression is to be prioritized, thebattery controller 107 executes step S112. As a result, the thirdallowable current is selected as the allowable current in thecharge/discharge control of the battery module 101.

After executing any one of steps S110 to S112, the battery controller107 completes the processing illustrated in the flowchart of FIG. 9 .

Hereinafter, effects of the present invention will be described withreference to FIGS. 10, 11, and 12 . FIG. 10 illustrates an example of achange in an allowable current in the case of using the conventionaltechnique. Generally in a battery system using a storage battery, as inthe case of the first allowable current, the second allowable current,and the third allowable current described above, there are a pluralityof allowable currents defined from different perspectives such as safetyof parts, safety of the storage battery, and a lifetime of the storagebattery. However, in a case where the minimum value of these allowablecurrents is used as an allowable current of a battery system as in therelated art, charge/discharge control cannot be performed beyond thisminimum allowable current. Therefore, as illustrated in FIG. 10 , insuch a case where the magnitude relationship of allowable currentsdiffers between low temperature and normal temperature and the thirdallowable current is lower than the first and the second allowablecurrents at normal temperature, charge/discharge control is alwaysperformed according to the minimum allowable current although there isno problem even if the charge/discharge current temporarily exceeds thethird allowable current. As a result, it is not possible to performcharging or discharging utilizing a range originally available at a roomtemperature, and the performance of the battery system cannot be exertedat the maximum when necessary.

On the other hand, FIG. 11 illustrates an example of a change in anallowable current in the case of using the present invention. In thepresent invention, as described in the above embodiment, the first, thesecond, and the third allowable currents defined from differentperspectives can be selectively used depending on the situation.Therefore, when a request for higher output is made to the batterysystem 100 in the case as described above, as illustrated in FIG. 11 ,it is possible to use a smaller one of the first allowable current andthe second allowable current as the allowable current to temporarilyincrease the allowable current. As a result, it is possible to make thefull use of the charge/discharge performance of the battery system.

FIG. 12 illustrates an example of a change in an allowable current whenthe present invention is more proactively utilized. For example, it isassumed that the battery system 100 is mounted to an electric vehiclesuch as a hybrid car and has a function that allows a driver to selectbetween a mode that gives priority to the lifetime of the battery module101 and a mode that gives priority to the traveling performance such asfuel consumption and acceleration performance. In such a case, asillustrated in FIG. 12 , the battery system 100 uses the third allowablecurrent as the allowable current when the driver selects the lifetimeprioritized mode and, when the traveling performance prioritized mode isselected, a smaller one of the first and the second allowable currentsis used as the allowable current. In this manner, it is also possible toemploy a system in which an allowable current is selected in accordancewith the selection of the driver.

According to the embodiment of the present invention described above,the following operational effects are obtained.

(1) The battery controller 107 includes the battery informationacquiring unit 201, the first allowable current calculating unit 202,the second allowable current calculating unit 203, and the thirdallowable current calculating unit 204. The battery informationacquiring unit 201 acquires information on the battery module 101 whichis a storage battery (step S101). The first allowable currentcalculating unit 202 calculates the first allowable current of thebattery module 101 in accordance with a rated value of a componentthrough which a current flows by charging or discharging of the batterymodule 101 (step S102). The second allowable current calculating unit203 calculates the second allowable current of the battery module 101 inaccordance with an SOC of the battery module 101 on the basis of theinformation acquired by the battery information acquiring unit 201 (stepS103). The third allowable current calculating unit 204 calculates thethird allowable current of the battery module 101 in accordance with anSOH of the battery module 101 on the basis of the information acquiredby the battery information acquiring unit 201 (step S104). In thismanner, it is possible to appropriately control the current of thebattery module 101 depending on the situation on the basis of thecalculation results of these allowable currents.

(2) The battery controller 107 further includes the allowable currentselecting unit 205 for selecting and outputting any one of the firstallowable current, the second allowable current, and the third allowablecurrent. In this manner, it is possible to select an appropriateallowable current depending on the situation and to use the allowablecurrent in the charge/discharge control of the battery module 101.

(3) In a case where the first allowable current is lower than the secondallowable current and the third allowable current (step S106), theallowable current selecting unit 205 selects the first allowable current(step S110), and the allowable current selecting unit 205 selects thesecond allowable current in a case where the second allowable current islower than the first allowable current and the third allowable current(step S111). In this manner, in a case where any one of the firstallowable current and the second allowable current is the lowest, thecharge/discharge control of the battery module 101 can be performed inaccordance with the lowest allowable current. Therefore, it is possibleto prevent failure of the battery system 100 and to maintain theperformance of the battery module 101.

(4) The allowable current selecting unit 205 determines whetherdeterioration suppression of the battery module 101 is to be prioritized(step S108). As a result, if it is determined that the deteriorationsuppression of the battery module 101 is to be prioritized, the thirdallowable current is selected (step S112). If it is determined that thedeterioration suppression of the battery module 101 is not to beprioritized, the first allowable current or the second allowable currentis selected (steps S110 and S111). In this manner, when thedeterioration suppression of the battery module 101 is to beprioritized, the charge/discharge control of the battery module 101 canbe performed in accordance with the third allowable current. Therefore,deterioration of the battery module 101 can be suppressed, and thelifetime can be secured.

Note that in the embodiment described above, the example in which thebattery controller 107 includes the allowable current selecting unit 205has been described; however, the function of the allowable currentselecting unit 205 may be implemented in the host controller 112. Inthis case, the battery controller 107 executes the processing of stepsS101 to S104 in FIG. 9 and outputs the values of the obtained firstallowable current, the second allowable current, and the third allowablecurrent to the host controller 112. The host controller 112 executes theprocessing of steps S105 to S112 on the basis of these allowablecurrents output from the battery controller 107 and selects one of thefirst allowable current, the second allowable current, and the thirdallowable current. Then, the charge/discharge control of the batterymodule 101 is performed in accordance with the selected allowablecurrent. Also in this manner, actions and effects similar to the abovecan be obtained.

The present invention is not limited to the above embodiment. Otheraspects conceivable within the range of technical ideas of the presentinvention are also included within the scope of the present invention.

REFERENCE SIGNS LIST

-   100: battery system-   101: battery module-   102: current sensor-   103: voltage sensor-   104: temperature sensor-   105: leakage current sensor-   106A, 106B: relay-   107: battery controller-   110: inverter-   111: load-   112: host controller-   201: battery information acquiring unit-   202: first allowable current calculating unit-   203: second allowable current calculating unit-   204: third allowable current calculating unit-   205: allowable current selecting unit

The invention claimed is:
 1. A storage battery control device,comprising: a processor programmed to execute a program stored inmemory, wherein the program causes the processor to: acquire informationon a storage battery; calculate a first allowable current of the storagebattery in accordance with a rated value of a component through which acurrent flows by charging or discharging of the storage battery;calculate a second allowable current of the storage battery inaccordance with a charging state of the storage battery based on theinformation; calculate a third allowable current of the storage batteryin accordance with a deterioration state of the storage battery based onthe information; determine whether deterioration suppression of thestorage battery is to be prioritized; select a smallest allowablecurrent of the first allowable current, the second allowable current andthe third allowable current, when determining that the deteriorationsuppression of the storage battery is to be prioritized; select asmaller allowable current of the first allowable current and the secondallowable current, when determining that the deterioration suppressionof the storage battery is not to be prioritized; and determine that thedeterioration suppression of the storage battery is not to beprioritized, while a higher output torque of an electric motor which isa load of the storage battery is requested.
 2. An electric vehicle,comprising: the storage battery control device according to claim 1; andan electric motor which is a load of a storage battery controlled by thestorage battery control device.
 3. The electric vehicle according toclaim 2, further comprising: a system including the storage batterycontrol device, wherein the system is configured to allow a driver ofthe electric vehicle to select any one of a first mode that givespriority to a lifetime of the storage battery and a second mode thatgives priority to a traveling performance of the electric vehicle. 4.The electric vehicle according to claim 3, wherein the system isconfigured to select the smaller allowable current of the firstallowable current and the second allowable current, when the second modeis selected by the driver.